Why does php need to set the time zone?

Since PHP5.0 rewrites the data() function, the current date and time function is 8 hours less than the system time; and the default setting of the PHP language is standard Greenwich Time (that is, using is the zero time zone), so to get the current local time, you must change the time zone setting in the PHP language.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Time is essential in life. The same is true in PHP. Time sometimes needs to be stored to record something or displayed in the browser.

In PHP, date and time are obtained through date and time functions. The date and time functions depend on the server's time setting. The server's time setting defaults to Greenwich Time (zero time zone time). If the time is not specifically set to a specific time zone, then the time obtained through the relevant PHP functions will be the zero time zone time. It is 8 hours less than Beijing time.

Division of time zones

The world is divided into 24 time zones. Each time zone has its own local time. At the same time, the The difference between local time is 1~23 hours, for example, the difference between local time in London, UK and local time in Beijing is 8 hours.

In the field of international radio communications, a unified time is used, called Universal Time Coordinated (UTC). UTC is the same as Greenwich Mean Time (GMT).

Time zone setting in PHP

Since PHP5.0 rewrites the data() function, the current date and time function is The system time is 8 hours less. The default setting of the PHP language is standard Greenwich Time (that is, the zero time zone is used), so to obtain the current local time, you must change the time zone setting in the PHP language.

There are three ways to set the time zone in PHP, which are introduced below.

1) Set in the configuration file

The configuration file of PHP is the php.ini file in the PHP installation directory, find and open it. Then search for date.timezone in the file,

replace the ; in front of ;date.timezone = with the / in PHP / has the same function and means a comment. Here we need to remove this ; and fill in the corresponding time zone identifier after the = in this sentence, as shown below:

[Date]
; Defines the default timezone used by the date functions
; http://php.net/date.timezone
date.timezone = Asia/Shangha

Some commonly used time zone identifiers and their meanings:

• Asia/Shanghai —— Shanghai

• Asia/Chongqing —— Chongqing

• Asia/Urumqi —— Urumqi

• Asia/Hong_Kong —— Hong Kong

• ##Asia/Macao — — Macau

• Asia/Taipei — Taipei

• Asia/Singapore — Singapore

• PRC - China Time Zone

# Tip: If you are in China, we can set the time zone to "Asia/Shanghai or PRC". Remember to restart the server after the setting is successful!

2) Use the ini_set() function to set the time zone

The ini_set() function in PHP can set the value of the specified configuration option. This configuration option will be in The new value is maintained while the script is running and restored when the script ends. The syntax format of the function is as follows:

ini_set($varname, $newvalue)

where $varname is the configuration option to be modified, and $newvalue is the new value of the configuration option.

Tips: The ini_set() function cannot modify all configuration options. You can view the configurations that can be modified by visiting "https://www.php.net/manual/zh/ini.list.php" options.

[Example] Use the ini_set() function to set the time zone.

<?php
header("Content-type:text/html;charset=utf-8");
ini_set(&#39;date.timezone&#39;, &#39;GMT&#39;);
echo &#39;当前的格林尼治时间为：&#39;.date(&#39;Y-m-d H:i:s&#39;,time()).&#39;<br>&#39;;
ini_set(&#39;date.timezone&#39;, &#39;Asia/Urumqi&#39;);
echo &#39;乌鲁木齐的当前时间为：&#39;.date(&#39;Y-m-d H:i:s&#39;,time()).&#39;<br>&#39;;
ini_set(&#39;date.timezone&#39;, &#39;Asia/Shanghai&#39;);
echo &#39;上海的当前时间为：&#39;.date(&#39;Y-m-d H:i:s&#39;,time());
?>

The running results are as follows:

当前的格林尼治时间为：2021-07-16 12:25:11
乌鲁木齐的当前时间为：2021-07-16 20:25:11
上海的当前时间为：2021-07-16 20:25:11

3) Use the date_default_timezone_set() function to set the time zone

The date_default_timezone_set() function in PHP can be used in scripts All time and date functions set a default time zone, and its syntax is as follows:

date_default_timezone_set($timezone_identifier)

The parameter $timezone_identifier is the time zone identifier, such as UTC (Greenwich Mean Time) or Europe/Lisbon (Portugal).

Since PHP5.1.0 (the date and time function has been rewritten in this version), if the time zone is illegal, each call to the date and time function will generate an E_NOTICE level error message. If you use the system setting or The TZ environment variable also generates E_STRICT level information.

[Example] Use date_default_timezone_set() function to set the time zone.

<?php
header("Content-type:text/html;charset=utf-8");
date_default_timezone_set(&#39;Asia/Urumqi&#39;);
echo &#39;乌鲁木齐的当前时间为：&#39;.date(&#39;Y-m-d H:i:s&#39;,time()).&#39;<br>&#39;;
date_default_timezone_set(&#39;Europe/Lisbon&#39;);
echo &#39;葡萄牙的当前时间为：&#39;.date(&#39;Y-m-d H:i:s&#39;,time()).&#39;<br>&#39;;
date_default_timezone_set(&#39;Asia/Shanghai&#39;);
echo &#39;上海的当前时间为：&#39;.date(&#39;Y-m-d H:i:s&#39;,time());
?>

The running results are as follows:

乌鲁木齐的当前时间为：2021-07-16 20:25:28
葡萄牙的当前时间为：2021-07-16 13:25:28
上海的当前时间为：2021-07-16 20:25:28

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